This application relates to the field of starter motor assemblies, and more particularly, to starter motor assemblies including two or more starter motors.
Starter motor assemblies are used to start vehicle engines, such as engines in heavy duty vehicles. The conventional starter motor assembly includes an electric motor, a solenoid, and a drive mechanism.
The starter motor is placed in operation when a user closes an ignition switch on the vehicle and energizes the solenoid. Energization of the solenoid moves a solenoid shaft (also referred to herein as the “plunger”) in an axial direction. Movement of the solenoid plunger closes electrical contacts, thereby delivering full power to the electric motor. Movement of the solenoid plunger also moves a pinion of the drive mechanism into engagement with the engine flywheel gear. The electric motor delivers torque to the pinion. The pinion, in turn, causes the flywheel to rotate, thereby cranking the vehicle engine.
Once the vehicle engine starts, the operator of the vehicle opens the ignition switch, de-energizing the solenoid assembly. As a result of this deenergization, the magnetic field that caused the plunger to move decreases and is overcome by a return spring, causing the plunger to return to its original position. As the plunger moves to its original position, the pinion is pulled away from the ring gear, and the vehicle engine operates free of the starter motor.
It is well-known by those having ordinary skill in the art that conventional starter systems have been susceptible to a problematic failure mode known in the art as “click-no-crank.” Click-no-crank refers to the axial face of the starter assembly pinion being driven into abutment with the interfacing axial surface of the engine ring gear, rather than the teeth of the ring gear and pinion becoming enmeshed. Such incidences involve energization of the starter solenoid assembly during operator activation of the switch, which results in the pinion-ring gear abutment (typically resulting in an audible “click”) blocking movement of solenoid switch contact plate, thereby preventing the switch from closing. Prolonged application of electrical power to solenoid assembly during an abutting condition between the pinion and ring gear can prevent the gears from meshing.
To address click-no-crank problems, some starter motors include a feature known as “soft-start.” Soft-start arrangements generally allow some limited power to be provided to the electric motor before the pinion engages the ring gear. As a result, the electric motor and pinion provide a “soft start” torque which helps the pinion clear any abutment with the ring gear, thus encouraging the pinion teeth to fully mesh with the ring gear teeth. However, this “soft-start” feature just mentioned is sometimes insufficient to overcome a click-no-crank event.
One of the historical challenges of dual and triple starter applications of the type subject of this disclosure has been the reliable engagement of all starters, virtually simultaneously. Dual and triple starter systems are typically provided in large heavy-duty equipment. For example, large unmanned generators with engines as large as 150 liters commonly have three starter assemblies to crank the engine. The starting operation of such generators can be entirely automated, being automatically triggered at the start of a power failure. In these circumstances, a click-no-crank event can result in automated cranking of the starters for 30 or 60 seconds, or whatever time interval is programmed, during which time a very high current passes through the coils, which can ultimately burn up the coils and cause the starter assemblies to fail. Similar problems may occur in other large industrial equipment, such as bulldozers, large trucks and other heavy duty equipment.
It would be desirable to achieve a cost-effective means for ensuring reliable and simultaneous engagement of all starters in a system using two or more starters that crank a single engine.